Method of producing a higher-purity metal

ABSTRACT

A method of producing a higher purity metal comprising the step of electrolyzing a coarse metal material by a primary electrolysis to obtain a primary electrodeposited metal, the step of electrolyzing the material with the primary electrodeposited metal obtained in the primary electrolysis step used as an anode to obtain a higher purity electrolyte for secondary electrolysis, and the step of further performing secondary electrolysis by employing higher purity electrolytic solution than said electrolytic solution with said primary electrodeposited metal as an anode, whereby providing an electro-refining method that effectively uses electrodes and an electrolyte produced in a plurality of electro-refining steps, reuses the flow of an electrolyte in the system, reduces organic matter-caused oxygen content, and can effectively produce a high purity metal.

FIELD OF THE INVENTION

The present invention relates to a method of producing higher puritymetal which effectively uses electrodes and an electrolyte produced in aplurality of electrolytic steps, and performs primary electrolysis andsecondary electrolysis, and, when necessary, tertiary electrolysis ofreusing the flow of an electrolyte in the system.

Moreover, the present invention further relates to a method of higherpurification effective in the higher purification of metal which reducesthe oxygen content caused by organic matter.

Further, the present invention additionally relates to a method ofproducing a higher purity metal in which, among the metals to beproduced in a higher purity pursuant to the foregoing methods, the totalcontent of alkali metal elements such as Na, K is 1 ppm or less; thetotal content of radio active elements such as U, Th is 1 ppb or less;the total content of transition metal or heavy metal elements such asFe, Ni, Cr, Cu, excluding cases of being contained as the principalcomponent, is 10 ppm or less; and the remaining portion thereof becomesa higher purity metal or other indispensable impurities.

In addition, the %, ppm, ppb used in the present specification all referto wt %, wtppm, wtppb.

BACKGROUND OF THE INVENTION

Conventionally, when producing a 4N or 5N (respectively implying 99.99wt %, 99.999 wt %) level higher purity metal, the electro-refiningmethod is often employed for the production thereof. Nevertheless, thereare many cases where approximate elements remain as impurities whenperforming electrolysis to the target metal. For example, in the case ofa transition metal such as iron, numerous elements such as nickel,cobalt and so on, which are also transition metals, are contained asimpurities.

When refining such crude metals of a 3N level, electrolysis is performedupon producing a higher purity liquid.

In order to obtain a higher purity metal in the foregoing electrolysis,it is necessary to employ a method of ion exchange or solvent extractionfor producing an electrolytic solution with few impurities.

As described above, the production of an electrolytic solution normallyrequires a refinement in advance prior to the electrolysis, and has ashortcoming in that the production cost therefor would become high.

OBJECT OF THE INVENTION

An object of the present invention is to provide an electrolysis methodwhich effectively uses electrodes and an electrolyte produced in aplurality of electrolytic steps, reuses the flow of an electrolyticsolution in the system, and thereby enables the effective production ofa higher purity metal. Another object of the present invention is tofurther provide a method of producing a higher purity metal whicheffectively uses electrodes and an electrolyte produced in a pluralityof electrolytic steps, reuses the flow of an electrolytic solution inthe system, reduces organic matter-caused oxygen content, and therebyenables the effective production of a higher purity metal.

SUMMARY OF THE INVENTION

In order to achieve the foregoing objects, it has been discovered thatby using an electrolytic solution, which was electrolyzed with theprimary electrodeposited metal obtained by the primary electrolytic stepas the anode, for the secondary electrolysis, the preparation of theelectrolytic solution can be simplified, and a higher purity metal canbe obtained pursuant to a plurality of electrolytic steps. In addition,by washing the electrolytic solution used above, the oxygen contentcaused by organic matter can be reduced.

Based on the foregoing discovery, the present invention provides:

-   1. A method of producing a higher purity metal comprising the step    of electrolyzing a coarse metal material by primary electrolysis to    obtain a primary electrodeposited metal, the step of performing    electrochemical dissolution with the primary electrodeposited metal    obtained in the primary electrolysis step as an anode or performing    acid dissolution to the primary electrodeposited metal in order to    obtain a higher purity electrolytic solution for secondary    electrolysis, and the step of further performing secondary    electrolysis by employing said higher purity electrolytic solution    for secondary electrolysis with said primary electrodeposited metal    as an anode;-   2. A method of producing a higher purity metal comprising the step    of electrolyzing a coarse metal material by primary electrolysis to    obtain a primary electrodeposited metal, the step of obtaining a    higher purity electrolytic solution for secondary electrolysis by    performing electrochemical dissolution or acid dissolution with the    primary electrodeposited metal obtained in the primary electrolysis    step as an anode, and the step of further performing secondary    electrolysis by employing said higher purity electrolytic solution    for secondary electrolysis with said primary electrodeposited metal    as an anode, wherein said electrolytic solution is liquid-circulated    in an activated carbon tank in order to eliminate organic matter in    the higher purity metal aqueous solution, thereby reducing the    oxygen content caused by said organic matter to 30 ppm or less;-   3. A method of producing a higher purity metal according to    paragraph 1 or paragraph 2 above, wherein the coarse metal has a    purity of 3N or less, the primary electrodeposited metal has a    purity of 3N to 4N excluding gas components such as oxygen, and the    higher purity metal obtained by the secondary electrolysis has a    purity of 4N to 5N or more;-   4. A method of producing a higher purity metal according to    paragraph 1 or paragraph 2 above, wherein the coarse metal has a    purity of 4N or less, the primary electrodeposited metal has a    purity of 4N to 5N excluding gas components such as oxygen, and the    higher purity metal obtained by the secondary electrolysis has a    purity of 5N to 6N or more;-   5. A method of producing a higher purity metal according to each of    paragraphs 1 to 4 above, wherein the electrolytic solution after the    secondary electrolysis step is used cyclically as the electrolytic    solution of the primary electrolysis;-   6. A method of producing a higher purity metal according to each of    paragraphs 1 to 5 above, wherein the electrolytic solution after the    primary electrolysis is either discharged outside the system or    reused after refining the liquid;-   7. A method of producing a higher purity metal according to each of    paragraphs 1 to 6 above, comprising the step of electrolyzing the    secondary electrodeposited metal obtained in the secondary    electrolysis step as an anode or performing acid dissolution to the    secondary electrodeposited metal in order to obtain a higher purity    electrolytic solution for tertiary electrolysis, and the step of    further performing tertiary electrolysis by employing said higher    purity electrolytic solution for tertiary electrolysis with said    secondary electrodeposited metal as an anode;-   8. A method of producing a higher purity metal according to each of    paragraphs 1 to 7 above, wherein, among the higher purity metal, the    total content of alkali metal elements such as Na, K is 1 ppm or    less; the total content of radio active elements such as U, Th is 1    ppb or less; the total content of transition metal or heavy metal    elements such as Fe, Ni, Cr, Cu is 10 ppm or less; and the remaining    portion thereof becomes a higher purity metal or other indispensable    impurities;-   9. A method of producing a higher purity metal according to each of    paragraphs 1 to 8 above, wherein the C content is 30 ppm or less and    the S content is 1 ppm or less; and-   10. A method of producing a higher purity metal according to each of    paragraphs 1 to 9 above, wherein the electrodeposited metal is    further dissolved in a vacuum or dissolved under an Ar atmosphere or    an Ar—H₂ atmosphere.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating the outline of the primary electrolysisstep, secondary electrolysis step, and the production step of theelectrolytic solution for the secondary electrolysis.

BEST DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is now described with reference to FIG. 1. FIG. 1is a diagram illustrating the outline of the primary electrolysis step,secondary electrolysis step, and the production step of the electrolyticsolution for the secondary electrolysis.

As shown in FIG. 1, a crude metallic material 3 (3N or less, or 4N orless) such as a metal scrap is placed in an anode basket 2 in theprimary electrolytic tank 1, and a primary electrodeposited metal isdeposited to a cathode 4 by electrolyzing the crude metallic material.Here, the initial electrolytic solution is prepared in advance. Purityof the primary electrodeposited metal pursuant to this primaryelectrolysis is 3N to 4N or 4N to 5N.

Next, the primary electrodeposited metal deposited to the cathode 4 iselectrolyzed as an anode 5 in the electrolytic tank 6 in order to obtaina secondary electrodeposited metal in a cathode 7.

In this case, the aforementioned primary electrodeposited metal as theanode 10 in a secondary electrolytic solution production tank 9 iselectrolyzed to produce the electrolytic solution 8. The cathode 11 inthis secondary electrolytic solution production tank 9 is insulated withan anion exchange membrane such that the metal from the anode 10 is notdeposited. Moreover, acid dissolution may be performed to the primaryelectrodeposited metal in a separate container in order to conduct pHadjustment.

As depicted in FIG. 1, the electrolytic solution 8 produced as describedabove is used in the secondary electrolysis. A higher purityelectrolytic solution can thereby be produced relatively easily, and theproduction cost can be significantly reduced. Further, the spentelectrolytic solution used in the secondary electrolytic tank 6 isreturned to the primary electrolytic tank 1 and used as the primaryelectrolytic solution.

The metal deposited to the cathode 7 in the secondary electrolytic tank6 has a purity of a 5N level or 6N level.

When seeking a higher purity, or when the target purity could not beobtained in the electro-refining process pursuant to the foregoingsecondary electrolysis, a tertiary electrolysis may be performed.

This step is similar to the case of the foregoing secondaryelectrolysis. In other words, a tertiary electrodeposited solution isproduced with the secondary electrodeposited metal deposited to thecathode in the secondary electrolysis as the anode of the tertiaryelectrolytic tank (not shown), or with the secondary electrodepositedmetal as the anode, and a tertiary electrodeposited solution isdeposited to the cathode of the tertiary electrolytic tank with thistertiary electrolytic solution as the electrolytic solution. The purityof the electrodeposited metal is sequentially improved as describedabove.

Similarly, the used tertiary electrolytic solution may be used as theelectrolytic solution of the secondary electrolytic tank or primaryelectrolytic tank.

The foregoing electrolytic solution may be entirely liquid-circulated inthe activated carbon tank in order to eliminate organic matter in thehigher purity metal aqueous solution. The oxygen content caused byorganic matter may thereby be reduced to 30 ppm or less.

The electro-refining of the present invention is applicable to theelectro-refining of metal elements such as iron, cadmium, zinc, copper,manganese, cobalt, nickel, chrome, silver, gold, lead, tin, indium,bismuth, gallium, and so on.

EXAMPLES AND COMPARATIVE EXAMPLES

Examples of the present invention are now described. These Examples aremerely illustrative, and the present invention shall in no way belimited thereby. In other words, the present invention shall include allother modes or modifications other than these Examples within the scopeof the technical spirit of this invention.

Example 1

An electrolytic tank as shown in FIG. 1 was used to perform electrolysiswith a 3N level massive iron as the anode, and a 4N level iron as thecathode.

Electrolysis was implemented with a bath temperature of 50° C.,hydrochloric electrolytic solution at pH2, iron concentration of 50 g/L,and current density of 1A/dm². Obtained thereby was electrolytic iron(deposited to the cathode) having a current efficiency of 90% and apurity level of 4N.

Next, this electrolytic iron was dissolved with a mixed solution ofhydrochloric acid and hydrogen peroxide solution, and made into anelectrolytic solution for secondary electrolysis by adjusting pH withammonia. Further, a second electrolysis (secondary electrolysis) wasimplemented with the 4N level primary electrolytic iron deposited to theforegoing cathode as the anode.

Conditions for the electrolysis are the same as those for the primaryelectrolysis. Electrolysis was implemented with a bath temperature of50° C., hydrochloric electrolytic solution at pH2, and ironconcentration of 50 g/L. As a result, obtained was electrolytic iron(deposited to the cathode) having a current efficiency of 92% and apurity level of 5N.

Analytical results of the primary electrolytic iron and secondaryelectrolytic iron are shown in Table 1. In the primary electrolyticiron, Al: 2 ppm, As: 3 ppm, Co: 7 ppm, Ni: 5 ppm, Cu: 1 ppm and Al: 2ppm existed as impurities. In the secondary electrolysis, however,excluding the existence of Co: 2 ppm, all other impurities were 1 ppm orless. Moreover, the used secondary electrolytic solution could bereturned to the primary electrolytic solution and used again.

As described above, superior results were yielded in that higher purity(5N) iron was produced with two electrolytic refining processes, and theproduction of electrolytic liquid could be facilitated.

TABLE 1 (ppm) Impurity Al As B Co Cr Ni Raw Material   20   30   15  35   1   20 4N    2    3  <1  7  <1    5 5N  <1  <1  <1  2  <1    1Impurity Zn Cu Al O C N Raw Material   15   12   25 200   30   30 4N  <1   1    2  50   10   10 5N  <1  <1  <1  50   10 <10

Example 2

Similar to aforementioned Example 1, an electrolytic tank as shown inFIG. 1 was used to perform electrolysis with a 3N level massive cadmiumas the anode, and titanium as the cathode.

Electrolysis was implemented with a bath temperature of 30° C., sulfuricacid of 80 g/L, cadmium concentration of 70 g/L, and current density of1A/dm². Obtained thereby was electrolytic cadmium (deposited to thecathode) having a current efficiency of 85% and a purity level of 4N.

Next, this electrolytic cadmium was electrolyzed with a sulfate bath,and made into an electrolytic solution for secondary electrolysis.Further, a second electrolysis (secondary electrolysis) was implementedwith the 4N level primary electrolytic cadmium deposited to theforegoing cathode as the anode.

Conditions for the electrolysis are the same as those for the primaryelectrolysis. Electrolysis was implemented with a bath temperature of30° C., sulfuric acid of 80 g/L, cadmium concentration of 70 g/L, andcurrent density of 1A/dm². As a result, obtained was electrolyticcadmium having a current efficiency of 92% and a purity level of 5N.

Analytical results of the primary electrolytic cadmium and secondaryelectrolytic cadmium are shown in Table 2. In the primary electrolyticcadmium, Ag: 2 ppm, Pb: 10 ppm, Cu: 1 ppm and Fe: 20 ppm existed asimpurities. In the secondary electrolysis, however, excluding theexistence of Pb: 2 ppm and Fe: 3 ppm, all other impurities were 1 ppm orless.

Moreover, similar to Example 1 above, the used secondary electrolyticsolution could be returned to the primary electrolytic solution and usedagain.

As described above, superior results were yielded in that higher purity(5N) cadmium was produced with two electrolytic refining processes, andthe production of electrolytic liquid could be facilitated.

TABLE 2 (ppm) Ag Pb Cu Zn Fe Raw Material 19 50 16 3 145 4N 2 10 1 <1 205N <1 2 <1 <1 3

Example 3

Similar to aforementioned Example 1, an electrolytic tank as shown inFIG. 1 was used to perform electrolysis with a 3N level massive cobaltas the anode, and a 4N level cobalt as the cathode.

Electrolysis was implemented with a bath temperature of 40° C.,hydrochloric electrolytic solution at pH2, cobalt concentration of 100g/L, current density of 1A/dm², and an electrolyzing time of 40 hours.Obtained thereby was approximately 1 kg of electrolytic cobalt(deposited to the cathode) having a current efficiency of 90%. Thepurity level thereof was 4N.

Next, this electrolytic cobalt was dissolved with sulfuric acid, andmade into an electrolytic solution for secondary electrolysis byadjusting to pH with ammonia. Further, a second electrolysis (secondaryelectrolysis) was implemented with the 4N level primary electrolyticcobalt deposited to the foregoing cathode as the anode.

Conditions for the electrolysis are the same as those for the primaryelectrolysis, and electrolysis was implemented with a bath temperatureof 40° C., hydrochloric electrolytic solution at pH2, and cobaltconcentration of 100 g/L. As a result, obtained was electrolytic cobalthaving a current efficiency of 92% and a purity level of 5N.

Analytical results of the primary electrolytic cobalt and secondaryelectrolytic cobalt are shown in Table 3. In the raw material cobalt,Na: 10 ppm, K: 1 ppm, Fe: 10 ppm, Ni: 500 ppm, Cu: 2.0 ppm, Al: 3.0 ppm,Cr: 0.1 ppm, S: 1 ppm, U: 0.2 ppb, and Th: 0.1 ppb existed asimpurities. In the primary electrolysis, however, excluding theexistence of Fe: 5 ppm and Ni: 50 ppm, all other impurities were 0.1 ppmor less.

Further, in the secondary electrolysis, excluding the existence of Fe: 2ppm and Ni: 3 ppm, all other impurities were less than 0.1 ppm, therebyrepresenting a significant decrease in impurities.

The used secondary electrolytic solution could be returned to theprimary electrolytic solution and used again.

As described above, superior results were yielded in that higher purity(5N) cobalt was produced with two electrolytic refining processes, andthe production of electrolytic liquid could be facilitated.

TABLE 3 (U, Th: ppb, Others: ppm) Na K Fe Ni Cu Raw Material 10 1 10 5002.0 Primary 0.1 <0.1 5 50 <0.1 Secondary <0.1 <0.1 2 3 <0.1 Al Cr S U ThRaw Material 3.0 0.1 1 0.2 0.1 Primary 0.1 <0.01 <0.1 <0.1 <0.1Secondary <0.01 <0.01 <0.1 <0.1 <0.1 Primary: primary electrolysisSecondary: secondary electrolysis

Example 4

Similar to aforementioned Example 1, an electrolytic tank as shown inFIG. 1 was used to perform electrolysis with a 4N level massive nickelas the anode, and a 4N level nickel as the cathode.

Electrolysis was implemented with a bath temperature of 40° C.,hydrochloric electrolytic solution at pH2, nickel concentration of 50g/L, current density of 1A/dm², and an electrolyzing time of 40 hours.Obtained thereby was approximately 1 kg of electrolytic nickel(deposited to the cathode) having a current efficiency of 90%. Thepurity level thereof was 5N.

Next, this electrolytic nickel was dissolved with sulfuric acid, andmade into an electrolytic solution for secondary electrolysis byadjusting to pH with ammonia. Further, a second electrolysis (secondaryelectrolysis) was implemented with the 5N level primary electrolyticnickel deposited to the foregoing cathode as the anode.

Conditions for the electrolysis are the same as those for the primaryelectrolysis, and electrolysis was implemented with a bath temperatureof 40° C., hydrochloric electrolytic solution at pH2, and nickelconcentration of 50 g/L. As a result, obtained was electrolytic nickelhaving a current efficiency of 92% and a purity level of 6N.

Analytical results of the primary electrolytic nickel and secondaryelectrolytic nickel are shown in Table 4. In the raw material nickel,Na: 16 ppm, K: 0.6 ppm, Fe: 7 ppm, Co: 0.55 ppm, Cu: 0.62 ppm, Al: 0.04ppm, Cr: 0.01 ppm, S: 1 ppm, U: 0.2 ppb, and Th: 0.1 ppb existed asimpurities. In the primary electrolysis, however, excluding theexistence of Fe: 2 ppm and Co: 0.2 ppm, all other impurities were 0.1ppm or less.

Further, in the secondary electrolysis, only Fe: 0.2 ppm existed, andall other impurities were less than 0.1 ppm, thereby representing asignificant decrease in impurities. The used secondary electrolyticsolution could be returned to the primary electrolytic solution and usedagain.

As described above, superior results were yielded in that higher purity(6N) nickel was produced with two electrolytic refining processes, andthe production of electrolytic liquid could be facilitated.

TABLE 4 (U, Tb: ppb, Others: ppm) Na K Fe Co Cu Raw Material 16 0.6 70.55 0.62 Primary 0.1 <0.1 2 0.2 <0.1 Secondary <0.1 <0.1 0.2 <0.1 <0.1Al Cr S U Th Raw Material 0.04 0.01 1 0.2 0.1 Primary <0.01 <0.01 <0.1<0.1 <0.1 Secondary <0.01 <0.01 <0.1 <0.1 <0.1 Primary: primaryelectrolysis Secondary: secondary electrolysis

Example 5

A 4N level raw material cobalt differing from the cobalt used above wasused to perform a separate primary electrolysis and secondaryelectrolysis, and, thereupon, the electrolytic solution was circulatedin the activated carbon tank in order to eliminate the organic matter inthe higher purity metal aqueous solution. The analytical results of theimpurity elements obtained pursuant to the aforementioned refining areshown in Table 5.

As impurities contained in the electrolytic cobalt pursuant to theforegoing primary electrolysis and secondary electrolysis, only Ti: 1.8ppm, Fe: 1.3 ppm and Ni: 4.2 ppm existed as impurities exceeding 1 ppm,and, excluding gas components such as oxygen, all other impurities wereless than 0.1 ppm, thereby representing a significant decrease inimpurities.

The used secondary electrolytic solution could be returned to theprimary electrolytic solution and used again. Although not shown inTable 5, oxygen was significantly eliminated with activated carbon, andwas reduced to 30 ppm or less.

As described above, superior results were yielded in that higher purity(5N) cobalt was produced with two electrolytic refining processes, andthe production of electrolytic liquid could be facilitated.

TABLE 5 Content: ppm (weight) Element Content Element Content ElementContent Li <0.005 As 0.03 Sm <0.005 Be <0.005 Se <0.05 Eu <0.005 B <0.01Br <0.05 Gd <0.005 F <0.05 Rb <0.005 Tb <0.005 Na <0.01 Sr <0.005 Dy<0.005 Mg <0.005 Y <0.001 Ho <0.005 Al 0.13 Zr <0.005 Er <0.005 Si 0.03Nb <0.01 Tm <0.005 P 0.3 Mo 0.12 Yb <0.005 S 0.17 Ru <0.01 Lu <0.005 Cl0.05 Rh <0.01 Hf <0.005 K <0.01 Pd <0.05 Ta <1 Ca <0.05 Ag <0.01 W <0.05Sc <0.001 Cd <0.05 Re <0.01 Ti 1.8 In <0.01 Os <0.005 V <0.001 Sn <0.01Ir <0.01 Cr 0.32 Sb <0.01 Pt <0.01 Mn <0.01 Te <0.05 Au <0.05 Fe 1.3 I<0.01 Hg <0.05 Co Matrix Cs <0.01 Ti <0.01 Ni 4.2 Ba <0.05 Pb <0.01 Cu0.05 La <0.1 Bi <0.005 Zn 0.03 Ce <0.005 Th <0.0001 Ga <0.05 Pr <0.005 U<0.0001 Ge <0.1 Nd <0.005

As described above, superior characteristics are yielded in that theprimary electrodeposited metal as an anode is electrolyzed in order toproduce a secondary electrolytic solution, and, further, by using suchprimary electrodeposited metal as the secondary electrolytic anode,higher purity electro-refining of 5N to 6N level is realized in additionto enabling the reduction of production costs of the secondaryelectrolytic solution of 4N to 5N level.

Moreover, a further superior effect is yielded in that the spentelectrolytic solution used in the secondary electrolytic tank isreturned to the primary electrolytic tank and may be used as the primaryelectrolytic solution, whereby the oxygen content can be reduced to 30ppm or less.

1. A method of producing a higher purity metal, comprising the steps of:(a) electrolyzing a crude metallic material by primary electrolysis toobtain a primary electrodeposited metal, (b) obtaining a higher purityelectrolytic solution for secondary electrolysis by performingelectrochemical dissolution using said primary electrodeposited metalobtained in the primary electrolysis of step (a) as an anode with acathode insulated by an ion exchange membrane, and (c) performing asecondary electrolysis by employing said higher purity electrolyticsolution for secondary electrolysis produced in step (b) with saidprimary electrodeposited metal produced in step (a) as an anode.
 2. Amethod according to claim 1, wherein said crude metallic material has apurity of 3N or less, wherein the primary electrodeposited metal has apurity of 3N to 4N excluding gas components which includes oxygen, andthe higher purity metal obtained by the secondary electrolysis has apurity of 4N to 5N or more.
 3. A method according to claim 1, whereinsaid crude metallic material has a purity of 4N or less, wherein theprimary electrodeposited metal has a purity of 4N to 5N excluding gascomponents which includes oxygen, and the higher purity metal obtainedby the secondary electrolysis has a purity of 5N to 6N or more.
 4. Amethod according to claim 1, wherein, after said secondary electrolysisstep, said electrolytic solution is used cyclically as the electrolyticsolution of the primary electrolysis.
 5. A method according to claim 1,wherein an electrolytic solution remaining after said primaryelectrolysis step is one of discharged and reused after being refined.6. A method according to claim 1, further comprising the steps of: (d)obtaining a secondary electrodeposited metal during said secondaryelectrolysis step; (e) electrolyzing said secondary electrodepositedmetal produced in step (d) to obtain a higher purity electrolyticsolution for tertiary electrolysis, and (f) performing a tertiaryelectrolysis by employing said higher purity electrolytic solution fortertiary electrolysis produced in step (e) with said secondaryelectrodeposited metal produced in step (d) as an anode.
 7. A methodaccording to claim 1, further comprising the steps of: (g) obtaining asecondary electrodeposited metal during said secondary electrolysisstep; (e) performing acid dissolution to said secondary electrodepositedmetal produced in step (d) to obtain a higher purity electrolyticsolution for tertiary electrolysis, and (f) performing a tertiaryelectrolysis by employing said higher purity electrolytic solution fortertiary electrolysis produced in step (e) with said secondaryelectrodeposited metal produced in step (d) as an anode.
 8. A methodaccording to claim 1, wherein the higher purity metal formed by themethod has a total content of alkali metal elements including Na and Kof 1 ppm or less, a total content of radio active elements including Uand Th of 1 ppb or less, a total content of transition and heavy metalelements including Fe, Ni, Cr and Cu of 10 ppm or less; and a remainingportion thereof being one of a higher purity metal and otherindispensable impurities.
 9. A method according to claim 1, wherein a Ccontent of the higher purity metal is 30 ppm or less and an S content is1 ppm or less.
 10. A method according to claim 1, further comprising astep of dissolving said primary electrodeposited metal in one of avacuum, an Ar atmosphere, and an Ar—H₂ atmosphere.
 11. A methodaccording to claim 1, wherein said electrolytic solution isliquid-circulated in an activated carbon tank to eliminate organicmatter in the higher purity metal aqueous solution, thereby reducing theoxygen content caused by said organic matter to 30 ppm or less.
 12. Amethod of producing a higher purity metal, comprising the steps of: (a)electrolyzing a crude metallic material by primary electrolysis toobtain a primary electrodeposited metal, (b) obtaining a higher purityelectrolytic solution for secondary electrolysis by performing aciddissolution with the primary electrodeposited metal obtained in theprimary electrolysis of step (a), and (c) performing a secondaryelectrolysis by employing said higher purity electrolytic solution forsecondary electrolysis produced in step (b) with said primaryelectrodeposited metal produced in step (a) as an anode, saidelectrolytic solution being liquid-circulated in an activated carbontank to eliminate organic matter in the higher purity metal aqueoussolution, thereby reducing the oxygen content caused by said organicmatter to 30 ppm or less.
 13. A method according to claim 12, whereinsaid crude metallic material has a purity of 3N or less, wherein theprimary electrodeposited metal has a purity of 3N to 4N excluding gascomponents which includes oxygen, and the higher purity metal obtainedby the secondary electrolysis has a purity of 4N to 5N or more.
 14. Amethod according to claim 12, wherein said crude metallic material has apurity of 4N or less, wherein the primary electrodeposited metal has apurity of 4N to 5N excluding gas components which includes oxygen, andthe higher purity metal obtained by the secondary electrolysis has apurity of 5N to 6N or more.
 15. A method according to claim 12, wherein,after said secondary electrolysis step, said electrolytic solution isused cyclically as the electrolytic solution of the primaryelectrolysis.
 16. A method according to claim 12, wherein anelectrolytic solution remaining after said primary electrolysis step isone of discharged and reused after being refined.
 17. A method accordingto claim 12, further comprising the steps of: (d) obtaining a secondaryelectrodeposited metal during said secondary electrolysis step; (e)electrolyzing said secondary electrodeposited metal produced in step (d)to obtain a higher purity electrolytic solution for tertiaryelectrolysis, and (f) performing a tertiary electrolysis by employingsaid higher purity electrolytic solution for tertiary electrolysisproduced in step (e) with said secondary electrodeposited metal producedin step (d) as an anode.
 18. A method according to claim 12, furthercomprising the steps of: (d) obtaining a secondary electrodepositedmetal during said secondary electrolysis step; (e) performing aciddissolution to said secondary electrodeposited metal produced in step(d) to obtain a higher purity electrolytic solution for tertiaryelectrolysis, and (f) performing a tertiary electrolysis by employingsaid higher purity electrolytic solution for tertiary electrolysisproduced in step (e) with said secondary electrodeposited metal producedin step (d) as an anode.
 19. A method according to claim 12, wherein thehigher purity metal formed by the method has a total content of alkalimetal elements including Na and K of 1 ppm or less, a total content ofradio active elements including U and of 1 ppb or less, a total contentof transition and heavy metal elements including Fe, Ni, Cr and Cu of 10ppm or less; and a remaining portion thereof being one of a higherpurity metal, and other indispensable impurities.
 20. A method accordingto claim 12, wherein a C content of the higher purity metal is 30 ppm orless and an S content is 1 ppm or less.
 21. A method according to claim12, further comprising a step of melting said primary electrodepositedmetal in one of a vacuum, an Ar atmosphere, and an Ar—H₂ atmosphere. 22.A method of producing a higher purity metal, comprising the steps of:(a) electrolyzing a crude metallic material by primary electrolysis toobtain a primary electrodeposited metal, (b) obtaining a higher purityelectrolytic solution for secondary electrolysis by performing aciddissolution of said primary electrodeposited metal obtained in theprimary electrolysis of step (a), and (c) performing a secondaryelectrolysis by employing said higher purity electrolytic solution forsecondary electrolysis produced in step (b) with said primaryelectrodeposited metal produced in step (a) as an anode.